The evolutionary origin of β-catenin-dependent germ layer specification

forthcoming

In the embryonic development of most animals, cell differentiation begins with the formation of three primary germ layers - ectoderm, endoderm, and mesoderm. A key regulator of this process is β-catenin, which activates the specification of the endoderm and mesoderm. Although β-catenin plays a central role in germ layer specification in a wide range of animals, we lack a detailed understanding of when this regulation emerged in animal evolution. By studying the embryonic development of the comb jelly Mnemiopsis leidyi, a member of the earliest branching animal lineage - Ctenophora, this project aims to determine whether β-catenin regulated endomesoderm specification in the last common ancestor of all animals. To understand the role of β-catenin in ctenophore germ layer specification, I will first characterize Mnemiopsis germ layers at the gene expression level using a single-cell sequencing approach. By comparing the results with data from other model organisms, I will determine whether Mnemiopsis germ layers are homologous to the ectoderm, endoderm, and mesoderm of other animals. Next, I will elucidate the spatial dynamics of β-catenin during germ layer specification by performing detailed immunofluorescence analysis using Mnemiopsis-specific anti-β-catenin antibodies. Finally, to assess the function of β-catenin signaling in ctenophore germ layer specification, I will analyze embryos with experimentally up- and downregulated β-catenin activity using morphological methods, gene expression analysis, and innovative 4D (3D time-lapse) microscopy. Through this research, CtenoGerm will deepen our understanding of how evolutionary changes in developmental programs have shaped the remarkable diversity of body forms across living species. By applying cutting-edge techniques in bioinformatics, molecular and developmental biology, and advancing leadership and management skills, the MSCA will be a transformative experience that will enhance my career and scientific growth.